The present invention relates to a drill for generating a hole in a work piece, preferably in a composite of at least a first material and a second material having a higher modulus of elasticity than the first material.
Known drills for drilling of composite materials have a shape similar to those of drills for wood comprising a centering tip and cutting edges arranged symmetrically therearound. A disadvantage with these drills is that they tear off the fibers arranged in the composite material, especially at the exit part of the hole when the drill penetrates the material. The fibers will therefore be forced outwardly at the exit part of the hole so that the hole obtains a very fringy end and/or delamination in the surrounding fiber layers. Furthermore the areas between the cutting tips and the centering tip will be filled up with cut material drilling of sandwich panels which disturbs the continous drilling in the material. The known drills are sensitive to shivering of the cutting edges. Furthermore, the center part of the drill cuts negatively, i.e. it presses the material before it, which prevents a clean cutting operation of the hole and raises the temperature in the cutting area so that the matrix material, for example epoxy, melts and flows out of the hole wall and thereby deteriorates the strength of the hole area.
The object of the present invention is to attain a drill for drilling of work pieces preferably of composite material through which shape the above-mentioned disadvantages are avoided.